This invention relates generally to the control of a high pressure fluid and, more particularly, to valves used to achieve pressure drops in fluid flow lines.
It is known in the art that objectionable noise is generated along with the desired reduction in pressure as expanding, pressurized fluid flows through the orifice in a control valve and that fluctuations in flow through the orifice have a marked influence on the generation of noise. Attempted solutions have included various devices for subdividing and confining the fluid in its flow through the orifice. These devices, commonly referred to as low noise trim, have not always performed as anticipated and it has, accordingly, been necessary to augment the installations with external retrofits such as insulation, fixed resistance elements, diffusers, silencers and, in some cases, enclosures. When added to the costs of a valve with low noise trim, such retrofits are not feasible from an economic standpoint. Furthermore, available low noise trim is such as to usually require an increase in the size of the valve for a given installation. External retrofits obviously require additional space not contemplated in the design stage.